Electric circuit



Y APl'il 17, 1945. z; o. sT. PALLEY 2,374,050

ELECTRIC CIRCUIT Filed Nov. 14, 1942 Inventor: v Zoltan 0. St. Pallas,

9 His Attorney.

Patented Apr. 11, 1945 andere ELECTRIC Gm Zoltan (D. St. liailey, Pittsiield, Mass., assigner t@ General Electric Company,

New Yori;

a corporation o@ application navenant ra, ifa/i2, sensi ist. atasco s crains. roi. rra-aim 'ihis invention relates to electric circuits and more particularly to improvements in reactor control circuits.

ns here used the term reactor means a device whose primary purpose is to insert either inductive or capacitive reactance into a circuit. It is generic to inductor and capacitor, the latter two being devices ,whose primary purpose is to insert inductance and capacitance respectively into a circuit.

There are many alternating-current circuits in which it is desirable to have adjustable reactance. For example, the power factor` of alternatingcurrent power circuits may be controlled by varying the amount of reactance which is connected across them.

In accordance with the present invention there is provided a novel and simple combination of a loadA-ratio-con'trol transformer and a multitapped reactor for varying the reactive load on a circuit in equal volt-ampere steps. By load ratio control is meant tap changing under load, and the invention is further characterized by a very efficient use of the tap-changing equipment. This is accomplished by having the tap-changing equipment operate at its maximum values of rupturing voltage and continuous current-carrying capacity for all positions of the tap-changing equipment.

An object of the invention is to provide a new and improved electric circuit.

brought out from the winding and terminating in stationarytap contacts il.

For supplying lagging wattless hva. to the circuit there is provided a reactor in the form of a plurality of equal-size serially-connected inductors t. The interconnections of these inductors are connected to taps t terminating in tap contacts I. The inductors E may either be separate devices or they may be combined into a single winding from which the taps 6 are brought out.

Clo-operating with the two sets oi tap contacts t and 1 is a pair of bridging contacts and 9 which are held in nxed spaced relation with respect to each other by an insulating member Ill. This bridging contact assembly is movable as a unit along the path bounded by the two sets of contacts. For example, the insulating spacer member Iii may be internally threaded so as to Another object of the invention is to provide a new and improved reactive volt-ampere control system.

A further object of the invention is to provide a new and improved power factor control system.

Still another object of the invention is to provide a new and improved load-ratio-control transformer and tap-changing reactor combination.

The invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

In the drawing Fig. 1 illustrates diagrammatically a simplified embodiment of the invention having inductors and Fig. 2 illustrates diagrammatically a. more practical modification using capacitors.

Referring now to the drawing and more particularly to Fig. 1, there is shown therein an alternating-current circuit I across which is connected an autotransformer 2. The winding of this autotransformer is divided into a plurality of equal'voltage sections by means of taps 3 is desired to change constitute a traveling nut with respect to a rotatably threaded shaft I2 having a hand wheel I3 or other suitable means for rotating it. One terminal of the inductor is permanently connected to one terminal of the autotransformer as by connecting it directly to one side of the circuit I.

The dimensions of all of the tap contacts are the same and their spacings are the same and are less than the distance between the outside edges of the bridging contacts 8 and 9 so that at least one of the bridging contacts 8 and 9 is always making a bridging connection between one tap contact l and its opposite tap contact 1.

The operation of Fig. 1 is as follows: Assume that circuit l is energized by any suitable source of alternating current (not shown) and that it the amount of wattless lagging current supplied by the circuit to the transformer reactor combination shown in the drawing. For example, assume it is desired to decrease the amount of such current. Under these circumstances the shaft I2 is rotated in such a rection as to cause the contact assembly 8-9 to move downwardly as viewed in the drawing. After a short movement in this direction the bridging contact 8 will break connection between the opposite tap contacts 4 and 1, thus simultaneously cutting out one section of the secondary winding of the autotransformer and one section of the reactance. However, as the voltages of the transformer sections are equal and the values of the induetors are equal, the current through the bridging contact 9 remains the same as was the current through the bridging contact 8. Continued downward movement will bring bothsets of bridging contacts into bridging relation with one pair of opposite tap contacts 4 and 1 which will produce no change in the circuit. Even l the bridging contact 9 will move out oi'co'ntact withl this pair of opposite tap contacts butagain there will be Further downward movement will then cause the bridging contact 8 simultaneously to make bridgingconnection between the lowermost` pair of opposite tap contacts d andll and finally the bridg-4 ing contact 8 will substantially simultaneously break the bridging connection between the next to the lowest opposite tap contacts d and l. The result is that the 'next to the lowermost section `of the secondary winding of the transformer is,

cut out of circuit and the next to the lowermost section of thereactor 6 is cut out of circuit, but here again through the bridging contacts .because the volthage impressed across the reactor through the there will be n o change in the currentc Furthermore, as the only voltage which is f astratto nosubstantial change and all of the l current will ow through the bridging contact 8.

.The contacts il and I9 dividually on traveling nuts which move along threaded rotating'shafts't'l, 22. 23 and 2l respec tively. These shafts are all driven by a common operating mechanism shown schematically at 2l.

through an arcing duty contactor 25, and the contacts i6 andI 26 are interconnected vthrough an arcing, duty contactor 2l. .These contactors are similarlyl driven by the operating mechanism 26 and all of the contactsand contactors are so interlocked that contactors il and i6 move simultaneously but only when arcing duty contactor 26 is open, and contactoxu i6. and 20 move simultaneously but only whenarcing duty contactor 2l is open. In this manner the ratio adjusting contacts il, mit duty.

In order to double the number of steps obtaintable with the equipment shown in Fig. Z-the transformer is provided with a tickler winding 28 whose voltage is hal! the voltage diierence between the taps 3 and the reactor is provided capacitor 29 whose capacitance the capacitors 5' or, in other words, its capacitive reactance is one-half lthe "capacitive reactance or the reactors 5'. These latter two devices enable voltages and reactance the same but lowers the eiective voltage of the secondary winding. Therefore, the reactiveV volt-amperes of the secondary winding decrease as the bridging contacts are moved downwardly and consequently the reactive volt-amperes of the primary winding of the transformer must also decrease, onlyl in that case the voltage is constant so it is the reactive lagging wattless current which decreases.

Similarly, rotating the driving wheel I8 in the opposite direction causes the bridging contacts to move upwardly, thereby successively to make bridging connection between opposite pairs of' tap' contacts whereby the effective voltage of the secondary winding of the transformer is increased in equal steps variable amounts of the reactor whose reactance also increases in equal steps so that the secondary current and the current handled by the switching means always remains constant. Also, as the voltage ruptured by the switching means remains constant, it follows that the switching .volt-ampere duty remains constant. However. upward movement of the bridging contacts causes the equipment as a whole to draw increasing amounts of lagging wattless current from the circuit l.

In Fig. 2 the winding 2 is one of a plurality of insulated windings of a transformer I4. Two other windings of this transformer are shown at I5 and i6. These windings may, for ex-ample, be

the primary and secondary windings of a power transformer whereby the winding 2 becomes the tertiary winding.

The reactor comprises a plurality of equal-size, serially-connected capacitors 5' provided with intermediate taps 6 and tap contacts l.

(Jo-operating with the tap contacts d is a double-finger ratio adjuster having two movable ratio adjusting contacts Il 'and I8 and similarly co-operating with the tap contacts 'I is another double-linger ratio adjuster having movable ratio adjusting contacts I9 and 20. These four ratio adjusting contacts may be moved in any suitable manner, such as by mounting them inand is applied across Acontacts Il and values to be obtained which are half way between those obtainable with the tap contacts alone.

The operation of Fig. 2 is as follows: With contactor 26 closed and contactor 2l open there will be four capacitors connected across four tap sections of the winding 2. If now contactor 2l is closed and contactor 26 is opened there will, in effect, be four and' one-half capacitors connected across four and one-half sections of the winding 2, thereby raising the capacitive voltamperes by an amount equal toone-half a step or tap change. If while contactor 21 is closed and contactor 26 is opened the ratio adjusting i9 are moved downwardly to the next tap contacts d and l respectively. then arcing contactor 21 is opened and contactor 26 is closed the connections will be such that ve capacitors will be connected across five tap Sections of lthe winding 2, thus further increasing the capacitive volt-amperes. VYIn this manner the tap changes may be madestep by step but twice as many steps may be obtained as there are taps.

From the above description it will be seen 4 that there has been provided an arrangement wherein standard (equal) transformer tap spacings and standard load-ratio-control mechanisms may be combined with a plurality of equal-size serially-connected reactors so as to obtain variations of reactive volt-amperes in equal steps, these steps being characterized by constant current and equal step voltage changes in the secondary circuit and constant voltage with equal step current variations in the primary circuit.

While there have been shown and described particular embodiments of this invention, it will be obvious to those skilled in the art that various and du need perform no arcing fore, it

and modiilcations can be made therein without departing from the invention and. thereis aimed in the appended claims to cover all such changes and modifications as iall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent oi the United States is:

l. In combination. a transformer winding. a plurality of serially-connected reactors which receive their entire energization from said transformer winding, and means for selectively connecting any desired number of said serially connected reactors across such variable portions of said winding that the voltage oi such portions is directly proportional to the reactance connected thereacross whereby the current in said connecting meanais constant.

2. In combination, a transformer having a winding divided into a plurality of equal-voltage serially-connected sections, a like number of equal-size reactors which receive their entire energization from said transformer winding, said reactorsv being connected in series, and means for selectively connecting any desired number of said reactors across the same number oi said sections.

3. In combination, a transformer having a winding provided with a set of electrically equalspaced taps, a plurality of electrically equal reactors which receive their entire energization from said transformer winding, said reactors being connected in series with each other, a set of taps connected to the interconnections between said reactors, and tap-changing means for selectively'interconnecting taps in the two sets, said interconnection being between pairs of taps whose combined voltage and reactance values are directly proportional to each other whereby the reactive current in said tap-changing means is constant for any pomtions thereof.

ZOLTAN O. ST. PALLEY. 

